This invention relates to television tilting apparatus that receives digital input signals corresponding to title information and generates video signals for displaying the information in readable form and, more particularly, to an apparatus of the stated type which is readily and efficiently adaptable to present languages which read right-to-left as well as languages such as English which read left-to-right.
Systems for converting digital title information into video signals that are suitable for display in readable form are currently in widespread use. These systems are employed, for example, to provide title information alone on a display screen, such as is typically done with financial data. Title information may also be generated for display in conjunction with conventional television picture information. This is generally accomplished by combining the video picture signal and the video title signal using known keying techniques.
A system that receives digitally coded characters and generates character video signals suitable for display using a television raster scanning pattern is disclosed in the U.S. Pat. No. 3,422,420. In this system the received digitally coded input character signals to be displayed in a row are stored in ordered positions in recirculating shift registers. Various timing signals, synchronized with the display scan, are generated in repetitive sequences and effectively divide the display scan into a plurality of "character space areas" of predetermined equal size. A character pattern or outline trace is formed in a character space area on the display device by blanking and unblanking the scanning beam as the beam traverses the display device. Thus, each character is formed on the display as a series of "slices" or "strokes" during successive scanlines. The character signals are read out of the recirculating shift registers one at a time, and a "character generator" subsystem generates the appropriate video stroke signals (blanking and unblanking commands) which are distinctive of the character being read out. The timing signals control the shifting and reading out of the character signals in the recirculating registers such that a new character signal is read out each time the display scan passes into a new character space area. After being read out, each character signal is restored in the recirculating registers to be recalled during the next display scanline when the next strokes of each character in the display row are generated. The retentivity of vision of the eye is relied upon to build up the impression of a complete character from the separate character strokes that are produced during each scanline.
In the U.S. Pat. No. 3,740.743 there is disclosed a television-compatible titling apparatus which generates proportionally spaced characters for display; i.e., characters which have different sized "character spaces". For example, a "W" has allotted a substantially larger character space than an "I". In the apparatus of the '743 patent the recirculating storage is shifted in response to spacer timing signals generated by a spacer detector which is responsive to the character signals and includes means for generating spacer timing signals which are a function of the width of the character to be instantaneously displayed. A stroke generator which is responsive to the timing signals and the spacer timing signals generates a stroke of a character being instantaneously displayed.
In both of the above-referenced television titling systems, the description is set forth in terms of a left-to-right display of characters, as is conventional for English and many language presentations. However, there are a number of important languages, such as Arabic, Hebrew, Farsi, etc., used in countries which have a need for television tilting equipment, that require a presentation of characters from right-to-left. It should be readily thought possible to design a television tilting system, modeled for example after the types of system previously referenced, which is capable of displaying characters from right-to-left. However, any such new design endeavor would ostensibly require substantial differences in the system design and structure, resulting in an attendant cost and inefficiency of having two different system structures which are not interchangeable. In this regard, it would be particularly useful to be able to have a basic system which could be used for both left-to-right and right-to-left languages without undue modification or expense. The problem of achieving this object is particularly acute in the type of titling system disclosed in the above-referenced U.S. Pat. No. 3,740,743 wherein proportionally spaced characters (which utilize different sized "character spaces") are employed. In such case, where the characters to be displayed right-to-left are of differing widths, characters cannot be readily exchanged from place to place without regard for their individual size (as might be the case in a non-proportional-spaced character system).
It is an object of the present invention to provide television titling system which is responsive to the stated problem.